1. Field of the Invention
The invention relates to a vane cell pump having a cam ring, supported in the housing, and a rotor with radial slots that is drivable by a drive shaft. Inserted into the radial slots are work slides that sealingly slide radially along in the cam ring. Between the cam ring, the rotor and the work slides, work chambers are formed that are defined in the axial direction by control plates. Built into the housing is a flow regulating valve, acted upon on one side by the delivery pressure against a spring force, which carries oil from a pressure chamber into a spray channel. A further orifice is also provided from the pressure chamber to an outlet channel.
2. Brief Description of the Invention
One such pump is known for instance from German Patent Application DE-A 41 08 126. In the control plate of this pump, an orifice with an orifice insert is provided between the pressure chamber and the outlet channel. This orifice brings about a descending characteristic curve of the flow rate over the rpm. In many cases, however, it is desirable to achieve a constant flow rate characteristic curve, for instance for use in power steering systems.
3. Summary of the Invention
The object of the invention is to attain a horizontal course of the characteristic curve. This object is attained by the characteristic features of the invention. The orifice seated in the outlet channel has a frustum flat face oriented toward the pressure chamber. By means of the frustum flat face, the inflow of oil into the orifice is varied in such a way that the desired constant, horizontal characteristic curve results. By means of the length of the orifice, a viscosity dependency is also attained, and as a result better cold-starting performance of the pump is obtained.